Summary
In weightlessness most subjects feel themselves, and see the visual surroundings, in either an upright or an upside-down orientation although the gravitational force vector is missing. According to a theory of gravity perception, these illusions of positional and visual verticality are assumed to be caused by the force-independent z-axis bias of vestibular and somatic graviceptors. This hypothesis is tested by comparison of measurements of the joint bias in normal gravity with reports of probands in space flight. The expected correlations between the sign of the biases and the occurrence of the respective illusions appear in fact to exist, as well as a negative correlation to incidences of space sickness. If confirmed in a larger sample, the presumed dependency may eventually afford a predictive test of both phenomena.
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Abbreviations
- SPV:
-
subjective positional vertical
- SVV:
-
subjective visual vertical
- SHP:
-
subjective horizontal position
- G :
-
magnitude of normalized gravitoinertial acceleration: actual acceleration (b) divided by g=981 cm s−2
- G :
-
b g −1
- G r :
-
normalized magnitude of acceleration exerted by sled centrifuge per centimeter radius: b g−1 r −1=G r −1=ω2 g −1=0.0145 G cm−1
- BA:
-
binaural axis of subject
- CA:
-
axis of sled centrifuge
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Mittelstaedt, H., Glasauer, S. Illusions of verticality in weightlessness. Clin Investig 71, 732–739 (1993). https://doi.org/10.1007/BF00209728
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DOI: https://doi.org/10.1007/BF00209728